Field of the Invention
The present invention relates to a display unit adapted to be mounted on various electronic apparatuses.
Description of the Related Art
As described in Japanese Patent Application Laid-Open No. 2011-203399, a display unit that combines a display panel and a control circuit for controlling the display panel is based on a well-known technique.
As shown in FIG. 1, a liquid-crystal display unit 1 comprises a display panel 10 for various liquid-crystal displays, a display control printed circuit board 2 for controlling a display signal to be transmitted to the display panel 10, and a fixing metal plate 8 for securing these elements. The illustration of a housing part of the display unit is omitted.
The display control printed circuit board 2 is mounted with a display controller 5 for generating a display control signal, a central processing unit (CPU) 3 for setting the display controller 5, and a memory 4 stored with set values for the display panel 10.
The display signal generated by the display control printed circuit board 2 is transmitted from a display signal connector 6 of the printed circuit board 2 to the display panel 10 by a display signal cable 7. The display panel 10 varies in resolution (number of pixels displayed on a screen), dot clock (clock as a reference for transfer per pixel), horizontal scanning frequency (updated number of lines capable of being displayed in each second), and vertical scanning frequency (number of screens updated in each second), depending on its size. For a correct display, therefore, it is necessary to identify the size of the display panel 10, generate the display signal conforming to the specifications of the display panel 10, and send it to the display panel 10. A correct display cannot be obtained if the display signal does not conform to the specifications of the display panel 10.
FIG. 2 shows a configuration and processing of the display control printed circuit board 2. The CPU 3 reads identification information (hereinafter referred to as “ID”) of the display panel 10 (numeral 11), reads a set value corresponding to the ID from the memory 4 (numeral 12), and sets the resolution, dot clock, horizontal scanning frequency, vertical scanning frequency, and the like for the display controller 5 (numeral 13). The display controller 5 generates the display signal according to the set values and transmits it to the display panel 10 (numeral 14).
Since the display panel 10 does not have its own ID, the CPU 3 cannot read any ID of the display panel 10 from the display signal connector 6 of FIG. 1. Instead, a circuit for identifying the ID of the display panel 10 should be mounted on the display control printed circuit board 2 so that the CPU 3 can read the ID. In this case, however, types required for the printed circuit board 2 are as many as those for the display panel 10 to be combined therewith.
If a large number of types are provided for the display control printed circuit board 2, the manufacture requires production control based on the types for the liquid-crystal display unit 1 to be shipped. In assembling the liquid-crystal display unit 1, moreover, the printed circuit board 2 may possibly be assembled by mistake.
Further, at the time of maintenance of the liquid-crystal display unit 1, the display control printed circuit board 2 varies depending on the size of the display panel 10 of the liquid-crystal display unit 1, so that the number of maintenance parts increases. In some cases, furthermore, the printed circuit board 2 may be wrongly mounted at the time of replacement.